Simultaneous measurement of pressure and temperature with a single FBG embedded in a polymer diaphragm

Abstract

This paper presents the development of a single polymer diaphragm-based fiber Bragg grating (FBG) sensor for simultaneous measurement of pressure and temperature. The FBG response is analyzed through a transient model for heat conduction and the pressure is estimated with the diaphragm and FBG strain, where the frequency difference between temperature and pressure variations were used to decouple both variables. Results show root mean squared error (RMSE) of 1.86 °C for the temperature analysis with constant pressure and 0.92 kPa for the pressure analysis with constant temperature. Experiments with variation of both temperature and pressure were conducted and the errors were higher than the ones with only temperature or pressure variations due to a residual cross-sensitivity. Therefore, the variation of both pressure and sensitivity leads to a RMSE of 3.88 °C and 5.13 kPa for temperature and pressure, respectively, which represent low errors of about 5% for both pressure and temperature.